1. Field of the Invention
This invention relates to automotive safety restraint systems. In particular, the invention relates to safety belt systems having webbing integrated airbags.
2. Description of Related Art
Numerous designs of passive and active automotive occupant restraint systems are known for enhancing occupant protection in the event of a vehicle impact. Passive systems are deployed with no action required by the occupant and include inflatable restraints, air bags for frontal and side impacts, and automatically deployed seat belt systems. Active systems, such as seat belts, have been used for many decades and are manually deployed by the occupant. The conventional seat belt system uses three points of connection with the vehicle structure or a vehicle seat and incorporates a lap belt portion for engaging the occupant's lower torso or pelvis, and a shoulder belt portion for engaging the occupant's upper torso or thorax. When engaged by the occupant, the seat belt restrains movement of the occupant in the event of a vehicle impact or rollover event.
One development in the area of seat belts includes inflatable seat belt systems. An inflatable seat belt system incorporates an airbag into a section of the belt webbing which is inflated by a gas, typically by means of a pyrotechnic inflator, to increase its size and volume. When an inflatable seat belt is activated, the airbag expands and the normally narrow seat belt webbing increases in area and volume to significantly reduce the contact pressure between the belt and the occupant during an impact event. The airbag also acts as a belt pretensioner since the inflatable section fills in the slack area between the occupant and the belt webbing.
However, conventional inflatable seat belts pose a number of design challenges. For example, typical inflatable seat belts dispose the inflatable section in the shoulder belt portion. The increased thickness of the inflatable belt section creates difficulties with cycling the webbing through a D-ring of the seat belt system. Additionally, occupants of different sizes draw differing amounts of the shoulder belt portion across their thorax, creating problems with properly positioning the inflatable belt section. Another disadvantage stems from the fact that they are primarily effective in frontal impact events. To protect against side impacts, an additional side impact or thorax airbag is often installed in the seat or another structure of the motor vehicle.
Motor vehicle designers are continually striving to provide enhanced performance of occupant protection systems while reducing the complexity and weight of vehicle systems while enhancing component packaging.